#!/usr/bin/node

const Readable = require('stream').Readable;

let c = 'a'.charCodeAt(0);

class MyReadable extends Readable{
  constrctor(){
    super.call(this);
  }

  _read () {
    rs.push(String.fromCharCode(c++));
    if (c > 'z'.charCodeAt(0)) rs.push(null)

  }
}
let rs = new MyReadable();
rs.pipe(process.stdout);
